CN110358946B

CN110358946B - Cu-Ni-Si copper alloy strip

Info

Publication number: CN110358946B
Application number: CN201910221346.7A
Authority: CN
Inventors: 中妻宗彦
Original assignee: Jks Metal Co ltd
Current assignee: Jks Metal Co ltd
Priority date: 2018-03-26
Filing date: 2019-03-22
Publication date: 2021-06-18
Anticipated expiration: 2039-03-22
Also published as: JP2019167612A; TWI715943B; KR20190112660A; CN110358946A; JP6762333B2; TWI724940B; TW202041690A; TW201940710A; KR102221879B1

Abstract

[ problem ] to provide a Cu-Ni-Si copper alloy strip having improved strength and high flatness, and a method for producing the same. [ solution ] A Cu-Ni-Si-based copper alloy strip containing Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, and the balance being Cu and unavoidable impurities, the electrical conductivity being 30% IACS or more and the tensile strength being 800MPa or more, and the average value of steepness is 0.5 or less and the variation rate of steepness represented by (deviation of steepness/average value of steepness) × 100 is 12% or less when measured at 5 or more points at a pitch of 25mm or less along a rolling orthogonal direction orthogonal to the rolling direction for the steepness in the rolling direction according to JCBA-T326-2014.

Description

Cu-Ni-Si copper alloy strip

Technical Field

The present invention relates to a Cu — Ni — Si-based copper alloy strip which is suitably used for manufacturing electronic components such as electronic materials.

Background

In recent years, with the miniaturization of IC packages, there is a demand for miniaturization and further increase in the number of pins of lead frames, various terminals of electronic devices, connectors, and the like. In particular, a structure called QFN (quad flat non-leaded package) has been developed in which electrode pads are arranged on a plane of an LSI package without exposing lead pins, and a demand for a multi-pin and a narrow pitch has been further increased.

Here, when forming the lead frame, it is necessary to perform etching processing on the lead frame material. In order to improve the productivity of the lead frame, it is required to increase the material width of the copper alloy strip to be used as a material. For this reason, the copper alloy strip for the lead frame is required to be a material having a wide width and excellent flatness, and particularly required to be flat after etching.

Further, these copper alloys are also required to have high strength and electric conductivity, and an age-precipitation type Cu — Ni — Si based copper alloy is used as a material for a lead frame (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open No. 4-231419.

Disclosure of Invention

Problems to be solved by the invention

Further, as a method of correcting the shape of the material to improve flatness, there is surface rolling, but since the material strength of the Cu — Ni — Si based copper alloy is high, the shape correction by the surface rolling cannot be sufficiently performed, and flatness may be poor. Patent document 1 describes that the strength of the material can be ensured by performing temper rolling after strain relief annealing, but the improvement of flatness is insufficient.

That is, the present invention has been made to solve the above problems, and an object thereof is to provide a Cu — Ni — Si based copper alloy strip having improved strength and high flatness.

Means for solving the problems

The present inventors have conducted various studies and, as a result, have found that: by performing intermediate strain relief annealing before finish rolling of a Cu-Ni-Si based copper alloy and controlling the finish degree of the finish rolling, the workability of the material can be improved without impairing the strength, and the flatness after the finish rolling can be improved.

That is, the Cu — Ni — Si-based copper alloy strip of the present invention contains Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, and the balance being Cu and unavoidable impurities, wherein when the steepness in the rolling direction is measured at 5 or more points at a pitch of 25mm or less along the rolling direction orthogonal to the rolling direction according to JCBA-T326-2014 at an electric conductivity of 30% IACS or more and a tensile strength of 800MPa or more, the steepness is 0.5 or less, and the variation ratio of the steepness represented by (the variation of the steepness/the average value of the steepness) × 100 is 12% or less.

Further, it is preferable to contain 0.005 to 0.8 mass% in total of at least one selected from the group consisting of Mg, Fe, P, Mn, Co and Cr.

Effects of the invention

According to the present invention, a Cu-Ni-Si-based copper alloy strip having high strength and high flatness can be obtained.

Drawings

Fig. 1 is a diagram showing an example of a plan view of material strain of a Cu — Ni — Si-based copper alloy strip according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a method of measuring the steepness.

Fig. 3 is a schematic view showing a method of measuring flatness in processing a lead frame.

Fig. 4 is a schematic view subsequent to fig. 3.

Detailed Description

Hereinafter, a Cu — Ni — Si based copper alloy strip according to an embodiment of the present invention will be described. In the alloy composition of the present invention,% represents mass% unless otherwise specified.

First, the reason for limiting the composition of the copper alloy strip will be described.

< Ni and Si >

By aging Ni and Si, Ni and Si are formed into fine Ni₂The precipitation particles of the intermetallic compound mainly containing Si significantly increase the strength of the alloy. In addition, with Ni in aging treatment₂Si precipitates and the conductivity is improved.

However, when the Ni concentration is less than 1.5% or the Si concentration is less than 0.4%, the desired strength cannot be obtained even when other components are added. When the Ni concentration exceeds 4.5% or the Si concentration exceeds 1.1%, sufficient strength can be obtained, but the conductivity is lowered. Therefore, the Ni content is set to 1.5 to 4.5%, and the Si content is set to 0.4 to 1.1%. Preferably, the Ni content is 1.6 to 3.0%, and the Si content is 0.4 to 0.7%.

< other elements >

Further, the alloy may contain 0.005 to 0.8% in total of at least one selected from the group consisting of Mg, Fe, P, Mn, Co and Cr for the purpose of improving the strength, heat resistance, stress relaxation resistance and the like of the alloy. If the total amount of these elements is less than 0.005%, the above-described effects are not produced, and if it exceeds 0.8%, the desired characteristics can be obtained, but the conductivity may be lowered.

< conductivity and tensile Strength TS >

The Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention has an electrical conductivity of 30% IACS or more and a tensile strength TS of 800MPa or more.

The electrical conduction and heat dissipation of the circuit such as the lead frame are increased by the increase in the processing capability accompanying the enhancement of the function of the semiconductor element, and therefore, the conductivity of the copper alloy strip is made 30% IACS or more.

The tensile strength TS is set to 800MPa or more in order to prevent deformation of the lead frame during wire bonding and to maintain the shape.

< steepness >

The average value Av of the steepness of the Cu-Ni-Si-based copper alloy strip according to the embodiment of the present invention in the rolling direction is 0.5 or less, and the deviation ratio DR of the steepness represented by (deviation D of the steepness/average value Av of the steepness) × 100 is 12% or less.

The steepness was defined in JCBA-T326-2014, and was determined by measuring the height change (waveform) in the rolling direction and the rolling direction perpendicular to the surface of the Cu-Ni-Si based copper alloy strip as shown in FIG. 1.

Specifically, as shown in fig. 2, the distance from the trough to the trough of the height profile curve 2 in the rolling direction is denoted as the wavelength L, and the distance from the straight line drawn from the trough to the peak is denoted as the peak height h, so that

Steepness (h/L) × 100 (%)

To indicate.

As shown in fig. 1, the height profile curve 2 in the rolling direction was measured at measurement points S1, S2, seeds and seeds at 5 or more points at a pitch P of 25mm or less in the direction perpendicular to the rolling direction, and the average value thereof was used as the average value Av of the steepness.

If the average value Av of the steepness is 0.5 or less, the flatness of the material during the processing of the lead frame is improved, and therefore, wire bondability is good and defects in the assembly process are reduced.

In addition, as described above, the deviation D of the steepness of 5 or more points was obtained, and the deviation ratio DR of the steepness was obtained by (deviation D of the steepness/average Av of the steepness) × 100 (%).

When the variation ratio of the steepness is 12% or less, it means that the elongation at the end and the intermediate elongation of the Cu — Ni — Si based copper alloy strip are suppressed, and the flatness is improved even if the width of the material is wide.

Examples of the method for controlling the average value Av of the steepness to 0.5 or less and the deviation ratio of the steepness to 12% or less include: the conditions for the strain relief annealing and the subsequent temper rolling are defined as described later.

< production of Cu-Ni-Si based copper alloy strip >

The Cu — Ni — Si-based copper alloy strip according to the embodiment of the present invention can be generally produced by subjecting an ingot to hot rolling, cold rolling, solution treatment, aging treatment, cold rolling after aging, strain relief annealing, and finish rolling in this order. The cold rolling before the solution treatment is not essential, and may be performed as needed. Further, cold rolling may be performed after the solution treatment and before the aging treatment, as necessary. Grinding, polishing, sandblasting, pickling, and the like for removing the surface scale may be appropriately performed between the above steps.

The solution treatment is a heat treatment for dissolving a silicide such as a Ni — Si compound in a solid solution in a Cu matrix and recrystallizing the Cu matrix. The solution treatment may be performed simultaneously by hot rolling.

In the aging treatment, a silicide which is solid-dissolved by the solution treatment is made to be Ni₂Fine particles of an intermetallic compound mainly containing Si are precipitated. The strength and the electric conductivity are improved by the aging treatment. The aging treatment can be performed, for example, at 375 to 625 ℃ for 1 to 50 hours, thereby improving the strength.

If the temperature and time of the aging treatment are less than the above ranges, Ni may be present₂The amount of Si precipitated is small and sufficient strength cannot be obtained. If the temperature and time of the aging treatment exceed the above ranges, precipitates may be coarsened and re-dissolved, and the strength and the electrical conductivity may not be sufficiently improved.

< Cold Rolling after aging >

Next, after the aging treatment, cold rolling may be performed at a reduction ratio of 40% or more (cold rolling after aging). By cold rolling after aging, work strain can be imparted to the material, and the strength can be improved.

If the cold rolling degree after aging is less than 40%, it may be difficult to sufficiently improve the strength. The working degree of cold rolling after aging is preferably 40-90%. If the degree of working exceeds 90%, the conductivity may be lowered by a strong working strain.

The cold rolling workability after aging is the rate of change in the thickness obtained by cold rolling after aging from the thickness of the material immediately before cold rolling after aging.

The thickness of the Cu-Ni-Si based copper alloy strip of the present invention is not particularly limited, and may be, for example, 0.03 to 0.6 mm.

< De-Strain annealing >

The cold rolling after aging is followed by a strain relief anneal. The strain relief annealing may be performed under a general condition, and may be performed, for example, at a holding time of 300 to 550 ℃ for 5 to 300 seconds. Thus, the ductility can be recovered by removing a part of the dislocations inside the material, and the shape correction by the surface finishing can be sufficiently performed. Particularly, it is desirable that Δ TS after the strain relief annealing is 10 to 30 MPa. If Δ TS is less than 10MPa, ductility is not sufficiently recovered, and shape correction by surface rolling is insufficient. When Δ TS exceeds 30MPa, workability is good, but strength is reduced by annealing, and TS may be less than 800 MPa.

Δ TS (mpa) is expressed by (i.e., tensile strength TS (mpa) of the material before the strain relief annealing) (i.e., tensile strength TS (mpa) of the material immediately after the strain relief annealing), and is usually Δ TS > 0.

< skin pass rolling >

And correcting the shape of the material by performing surface finish rolling with the degree of processing of 0.4-1.6% after the strain relief annealing. If the finish degree of the finish rolling is less than 0.4%, sufficient shape correction cannot be performed, rolling strain remains, and flatness may not be improved. If the degree of working exceeds 1.6%, the material may be strained again under high pressure, and thus the flatness may not be improved.

< Final De-Strain annealing >

A final de-strain anneal may be performed after the skin pass. The final de-straining annealing may be performed under the same conditions as the above-described de-straining annealing before the skin pass, thereby enabling elastic recovery of the material that is reduced in the skin pass.

[ example 1]

Samples of each example and each comparative example were produced as follows.

Electrolytic copper was used as a raw material, and a copper alloy having a composition shown in table 1 was melted and cast in an atmospheric melting furnace. The ingot was hot-rolled at 950 ℃ until the thickness became 10 mm. After hot rolling, the steel sheet was ground to obtain a material having a width of 600mm, and then cold rolling, solution treatment and aging treatment were performed in this order.

Next, the plate was cold-rolled after aging at the working degrees shown in Table 1 until the plate thickness became 0.152 mm. Further, the strain relief annealing was performed under the conditions (Δ TS) shown in table 1, and then, the finish rolling was performed at the working degree shown in table 1, and then, the final strain relief annealing was performed to obtain a sample.

< conductivity (% IACS) >

The obtained sample was measured for electrical conductivity (% IACS) at 25 ℃ by the 4-terminal method based on JIS H0505.

< Tensile Strength (TS) >

The Tensile Strength (TS) in the direction parallel to the rolling direction of each of the obtained samples was measured by a tensile tester in accordance with JIS-Z2241. First, a test piece according to JIS13B was prepared from each sample using a press machine so that the tensile direction was the rolling direction. The conditions for the tensile test were: the test piece has a width of 12.7mm, a room temperature (15-35 ℃), a stretching speed of 5mm/min and a measurement length of 50 mm.

< steepness >

The steepness in the rolling direction at 5 points in total was measured using a noncontact three-dimensional measuring machine according to JCBA-T326-2014 with the center in the rolling direction being the center and the pitch of 25mm for the obtained sample (width in the rolling direction at right angle of 600mm and length in the rolling direction of 1000 mm).

Then, as described above, the average value Av of the steepness and the deviation D of the steepness are obtained, and the deviation ratio DR of the steepness (deviation D of the steepness/average value Av of the steepness) × 100 (%) is calculated.

< flatness during lead frame processing >

Using the obtained sample (width in the rolling direction was 600mm, length in the rolling direction was 20 mm), a slit pattern having a lead length of 8mm, a width of 0.25mm, and a lead pitch of 0.5mm was formed by spray etching of an etching solution of 47 Baume at 40 ℃ on one surface of the sample as shown in FIG. 3. In this slit pattern, a plurality of leads LE are arranged adjacent to each other in a comb shape in the rolling orthogonal direction, and the inner lead portion of the lead frame is simulated.

Next, as shown in fig. 4, the etched lead frame was placed on a stage T with the etching spray surface facing upward, and the height HL of each lead LE from the stage T was measured as viewed from the extending direction of the lead LE. When 150% of the thickness t of the leads LE is defined as a reference height HS and the length LR in the rolling orthogonal direction between the leads LE in the region where the heights HL are continuously equal to or less than HS is 550mm or more, the flatness of the lead frame is considered to be excellent even if the lead frame is processed.

The results are shown in Table 1.

[ Table 1]

As is clear from table 1: in each example in which the variation rate of the steepness was 12% or less, the tensile strength was 800MPa or more, the average value of the steepness was 0.5 or less, and the variation rate of the steepness was 12% or less, and the flatness during the lead frame processing (after etching) was excellent.

In the case of comparative example 1 in which Δ TS at the time of the strain relief annealing was less than 10MPa, the average value of steepness exceeded 0.5, the rate of variation of steepness exceeded 12%, and the flatness at the time of lead frame processing was poor.

In comparative example 2 in which Δ TS at the time of the strain relief annealing exceeded 30MPa, the tensile strength was less than 800 MPa.

In the case of comparative example 3 in which the finish degree of the finish rolling exceeds 1.6%, deformation occurs at the time of the finish rolling, the steepness exceeds 0.5, and the variation rate of the steepness exceeds 12%. Therefore, the flatness is poor when the lead frame is processed.

In the case of comparative example 4 in which the finish degree of the surface finish rolling was less than 0.4%, since the shape correction was not sufficiently performed by the surface finish rolling, the steepness exceeded 0.5, and the deviation ratio of the steepness exceeded 12%. Therefore, the flatness is poor when the lead frame is processed.

In comparative example 5 in which the cold rolling workability after aging was less than 40%, the tensile strength was less than 800 MPa.

In comparative example 6 in which the contents of Ni and Si exceed the predetermined ranges, the conductivity was less than 30% IACS.

In comparative example 7 in which the contents of Ni and Si were less than the predetermined ranges, the tensile strength was less than 800 MPa.

In the case of comparative example 8 in which the total content of the additive elements exceeds 0.8 mass%, the conductivity was less than 30% IACS.

Claims

1. A Cu-Ni-Si-based copper alloy strip containing Ni: 1.5 to 4.5 mass%, Si: 0.4 to 1.1 mass%, and the balance consisting of Cu and unavoidable impurities,

an electric conductivity of 30% IACS or more and a tensile strength of 800MPa or more,

according to JCBA-T326-2014, when the steepness in the rolling direction is measured at 5 or more positions at a pitch of 25mm or less in the direction perpendicular to the rolling direction, the average value of the steepness is 0.5 or less, and

the deviation ratio of the steepness represented by (deviation of the steepness/average value of the steepness) × 100 is 12% or less.

2. The Cu-Ni-Si based copper alloy strip according to claim 1, further comprising 0.005 to 0.8 mass% in total of at least one selected from the group consisting of Mg, Fe, P, Mn, Co and Cr.